2015-07-31T15:21:42ZSpectroscopy and theory of cis-trans isomerization in the S₁ state of acetylenehttp://hdl.handle.net/1721.1/82336
Spectroscopy and theory of cis-trans isomerization in the S₁ state of acetylene
Changala, P. Bryan (Peter Bryan)
This thesis consists of parallel experimental and theoretical studies of the rovibrational structure and dynamics of the Si state of acetylene, C2H2 . This small molecule is a prototypical system for the study of cis-trans isomerization, the barrier to which is moderately low in the Si state, presenting the opportunity to achieve a complete understanding of the global rovibrational dynamics of an isomerizing system. Our analysis of the spectra of ungerade vibrational levels in the region 45800-46550 cm-1 extends the complete assignment of trans vibrational levels to 4300 cm-1 above the Si electronic origin. These exhaustive assignments have enabled the identification of two new cis vibrational states. Reduced dimension rovibrational variational calculations have been carried out to aid in the characterization of spectroscopic signatures and patterns associated with the isomerization process. Such effects include the decoupling of the vibrational polyads that involve the low-energy bending modes [nu]4 and [nu]6 and the large cross-anharmonicity of modes [nu]3 and [nu]6, the combination bands of which follow the isomerization path toward the half-linear transition state. Additionally, we focus on predictions for the K-staggering observed in both cis and trans levels caused by tunneling through the isomerization barrier. The detailed patterns of these staggerings make possible a direct empirical distinction between different possible isomerization mechanisms. We also present an empirical model which analyzes the vibrational level structure along the isomerization path. This model enables the direct spectroscopic characterization of the energy of the transition state, the qualitative structure and width of the isomerization barrier, and the curvature of the nuclear potential surface in directions orthogonal to the isomerization path. This type of analysis is generalizable to other systems, potential surfaces of which contain stationary points and thus provides a powerful new tool for studying transition states via frequency domain spectroscopy.
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Chemistry; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.; Cataloged from PDF version of thesis.; Includes bibliographical references (p. 95-99).
2013-01-01T00:00:00ZTargeted sensors for investigating mobile Zinc in biologyhttp://hdl.handle.net/1721.1/82335
Targeted sensors for investigating mobile Zinc in biology
Chyan, Wen, S.B. Massachusetts Institute of Technology
Chapter 1. Sensing Strategies for Detection of Mobile Zinc. Mobile zinc plays important physiological roles in areas such as the hippocampus, prostate, and pancreas. A better understanding of the distribution of intracellular mobile zinc could provide insight into the pathology of diseases including prostate cancer and Alzheimer's disease, both of which have been linked to abnormal mobile zinc levels. Accordingly, a palette of spatially-specific mobile zinc sensors is needed to investigate mobile zinc in important areas such as the mitochondria or zinc vesicles in neurons. Instead of repeating the de novo sensor design process for each target, a modular approach was developed to take advantage of the existing library of sensors and enable rapid creation of targeted probes. Chapter 2. Targeting Fluorescent Zinc Sensors to the Mitochondria Using Triphenylphosphonium Ions. Mitochondrial mobile zinc plays an important, although poorly understood, role in prostate cancer. To investigate the biology of zinc in the mitochondria, constructs incorporating fluorophores and the mitochondria-targeting triphenylphosphonium (TPP) moiety were tested and used to study sensor uptake and localization to the mitochondria. Chapter 3. Peptide-based Targeting of Fluorescent Zinc Sensors to the Plasma Membrane and Intracellular Targets in Live Cells. Peptide-sensor constructs were explored as a modular method of targeting sensors to specific locations. Taking advantage of the synthetic flexibility and targeting advantages of peptide-sensor constructs, mobile zinc sensors were directed to the exterior of the plasma membrane and to intracellular targets. A series of peptide-sensor constructs were created to further investigate fluorophore effects on sensor uptake and localization. Chapter 4. Improvement of Sensor Uptake, Localization, and Photophysics Through Acetylation of Fluorescein-based Sensors. A generalizable strategy for improving the uptake and photophysics of mobile zinc probes was explored. The ZPI-TPP sensor construct was modified by one-step acetylation of phenolic oxygen atoms. This modification dramatically improved photophysics and eliminated problems with membrane impermeability that would otherwise result in endosomal sequestration. The resulting DA-ZP1-TPP sensor was highly selective for zinc, resilient against cellular esterases, and, most importantly, was specifically targeted to the mitochondria.
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013.; Vita. Cataloged from PDF version of thesis.; Includes bibliographical references.
2013-01-01T00:00:00ZSome attempts to prepare triphenylcarbinyl p-toluenesulfonate, trityl tosylatehttp://hdl.handle.net/1721.1/79471
Some attempts to prepare triphenylcarbinyl p-toluenesulfonate, trityl tosylate
Killheffer, John Vincent
Thesis (B.S.) Massachusetts Institute of Technology. Dept. of Chemistry, 1950.; MIT copy bound with: The structures of adducts from the reactions of chloroprene with methyl acrylate and methyl methacrylate, conversion of vinyl-type halides to keto-compounds / Peter Paul Klemchuk. 1950. -- The development of rapid ion exchange separations to study genetic relations among rare earth activities / Paul Kruger. 1950. -- An attempted synthesis of 1,1-dimethyl-1-silico-cyclopropane / Daniel P. Lundgren. 1950. -- The infrared absorption spectra of solutions of amine hydrochlorides in non-polar solvents / Richard E. Merrifield. 1950. -- The polarography of carbon tetrachloride / Edward Bernard Mikrut. 1950. -- Ionization of polymethacrylic acid / Robert L. Miller. 1950.; Bibliography: leaves 21-24.
1950-01-01T00:00:00ZProgress towards the synthesis of tetracyclic heteroaromatic compounds via tandem benzannulation-cyclization strategieshttp://hdl.handle.net/1721.1/78512
Progress towards the synthesis of tetracyclic heteroaromatic compounds via tandem benzannulation-cyclization strategies
Mamaliga, Galina
A tandem benzannulation-cyclization strategy was successfully applied to the synthesis of a tetracyclic heteroaromatic compound expected to have interesting electronic properties. Benzannulation of a diazo ketone and a ynamide yielded a highly substituted aniline that was cyclized to indole according to protocols developed in our laboratory previously.
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Chemistry, February 2012.; Cataloged from PDF version of thesis.; Includes bibliographical references.
2012-01-01T00:00:00Z